Because of its deep roots in prescientific craftsmanship, the language used in describing the stock refining process has been often characterized by ambiguities, inconsistencies, and variations. In their preliminary attempts to build mathematical models of the refining process or otherwise delineate interrelationships involved, members of the Stock Preparation Committee have become increasingly aware of sources of confusion that could be eliminated through the medium of a list of definitions approved by the committee in deliberate session and published with the hope that it will be accepted by industry when its effectiveness is appreciated by the larger body of papermakers and students of the art. It is anticipated that the proving ground of this list will be its applicability in future work of the committee and others engaged in analysis of the fiber refining process. The glossary has been limited to terms used to describe functions and stock qualities resulting therefrom. Equipment nomenclature should constitute another distinct body of definitions that may be prepared if needed.